Unable to create a pull request when the desination repository is empty (BB-8226)

I have to repositories: fortedesenvolvimento/bingoroom.server and rafaelsoares/bingoroom.server (forked from the former). When I try to make a Pull Request, I get a "loading..." gif that stays there forever, and I'm unable to choose where to make to pull request to from the dropdown menu.

Attached is a screenshot of the problem.

Thanks